1. Field of Invention
The present invention relates to classifying particles and, in particular, to utilizing time-based fluorescence techniques to characterize the biological nature of aerosol particles.
2. Discussion of Related Art
Detection of biological aerosol particles or bioaerosols can be important in many fields including, for example, agriculture, food processing, public health, worker safety, resident/patient safety, disease prevention and eradication, emergency response, homeland defense and counterterrorism, and military base and force protection because bioaerosols may be harmful to human or animal health. Intrinsic particle fluorescence is a method that be utilized to distinguish biological particles from non-biological background particles. However, atmospheric pollutants may also fluoresce and can cause fluorescence-based instruments to register false positive indications. Various systems and methods can be utilized to characterize the nature of aerosol particles. For example, common detectors, cue detectors or trigger detectors, are typically optical scattering particle counters equipped with laser-induced fluorescence detection devices. Typically in such a system, an ultraviolet laser beam excites a particle to be examined. The particle's resultant fluorescence can be dispersed into two detection channels, roughly divided between ultraviolet and visible wavelengths. The particle is thereafter classified as threatening or non-threatening according to its relative position on a three-dimensional graph of UV intensity, visible intensity, and scattering intensity. While progress has been made these detectors still suffer from potential interference due to background fluorescence.
For example, Brewer, in U.S. Pat. No. 3,566,114, discloses a method and means for detection of microorganisms in the atmosphere. Macias et al., in U.S. Pat. No. 4,013,888, disclose a monitor for atmospheric pollutants. Javan, in U.S. Pat. No. 4,561,010, discloses a method and apparatus for fluorescent sensing. Hirako et al., in U.S. Pat. No. 5,158,889, disclose a biological cell sorter. Ho, in U.S. Pat. Nos. 5,701,012 and 5,895,922, discloses fluorescent biological particle detection systems. Gillespie et al., in U.S. Pat. No. 5,828,452, disclose a spectroscopic system with a single converter and method for removing overlay in time of detected emissions. Zborowski et al., in U.S. Pat. No. 6,142,025, disclose a method for determining particle characteristics. Fukuda et al., in U.S. Pat. No. 6,165,740, disclose a method and device for flow-cytometric microorganism analysis. Jeys et al., in U.S. Pat. No. 6,194,731, disclose a bio-particle fluorescence detector. Ray et al., in U.S. Pat. No. 6,608,677, disclose a mini-LIDAR sensor for the remote stand-off sensing of chemical/biological substances and methods for sensing same. Simonson et al., in U.S. Pat. No. 6,617,591, disclose a method for remote detection of trace contaminants. Carrión et al., in U.S. Pat. No. 6,630,299, disclose fluorescence detection. Gillispie, in U.S. Patent Application Publication 2002/0158211, disclose a multi-dimensional fluorescence apparatus and method for rapid and highly sensitive quantitative analysis of mixtures.